Exposure apparatus, maintenance method therefor, semiconductor device manufacturing method using the apparatus, and semiconductor manufacturing factory

ABSTRACT

An exposure apparatus includes a reticle stage which holds a reticle, a projection optical system which projects a pattern of the reticle onto a substrate, a reticle surface plate which is a base plate disposed between the reticle and the projection optical system and which supports the reticle stage. The reticle surface plate has an opening for transmitting exposure light. The exposure apparatus further includes a sheet glass set on the reticle surface plate so as to separate a space inside the opening of the reticle surface plate from a space above the reticle surface plate.

This application is a continuation of application Ser. No. 10/622,143filed Jul. 18, 2003, now U.S. Pat. No. 6,891,593 which is a continuationof application Ser. No. 09/986,918 filed Nov. 13, 2001, U.S. Pat. No.6,757,048 B2.

FIELD OF THE INVENTION

The present invention relates to an exposure apparatus for projecting amask pattern onto a photosensitive substrate via a projection opticalsystem, a maintenance method for the apparatus, a semiconductor devicemanufacturing method using the apparatus, and a semiconductormanufacturing factory.

BACKGROUND OF THE INVENTION

A conventional manufacturing process for manufacturing a semiconductorelement such as an LSI or VLSI formed from a micropattern uses areduction type projection exposure apparatus for transferring byreduction projection a circuit pattern drawn on a mask such as a reticleonto a substrate coated with a photosensitive agent. With an increase inthe packaging density of semiconductor elements, demands have arisen forfurther micropatterning. Exposure apparatuses are coping withmicropatterning along with the development of a resist process.

Methods of increasing the resolving power of the exposure apparatusinclude a method of changing the exposure wavelength to a shorter one,and a method of increasing the numerical aperture (NA) of the projectionoptical system.

As for the exposure wavelength, a KrF excimer laser with an oscillationwavelength of 365-nm i-line to recently 248 nm, and an ArF excimer laserwith an oscillation wavelength around 193 nm have been developed. Afluorine (F₂) excimer laser with an oscillation wavelength around 157 nmis also under development.

An ArF excimer laser with a wavelength around ultraviolet rays,particularly, 193 nm, and a fluorine (F₂) excimer laser with anoscillation wavelength around 157 nm are known to have an oxygen (O₂)absorption band around their wavelength band.

For example, a fluorine excimer laser has been applied to an exposureapparatus because of a short wavelength of 157 nm. The 157-nm wavelengthfalls within a wavelength region called a vacuum ultraviolet region.Light in this wavelength region is greatly absorbed by oxygen molecules.In other words, light hardly passes through the air. Thus, the fluorineexcimer laser can only be applied in a low-oxygen-concentrationenvironment. According to the reference “Photochemistry of SmallMolecules” (Hideo Okabe, A Wiley-Interscience Publication, 1978, p.178), the absorption coefficient of oxygen to 157-nm light is about 190atm⁻¹ cm⁻¹. This means when 157-nm light passes through a gas at anoxygen concentration of 1% at one atmospheric pressure, thetransmittance per cm is onlyT=exp(−190×1 cm×0.01 atm)=0.150.

In such an exposure apparatus using an ArF excimer laser with awavelength around ultraviolet rays, particularly, 193 nm, or a fluorine(F₂) excimer laser with a wavelength around 157 nm, an ArF excimer laserbeam or fluorine (F₂) excimer laser beam is readily absorbed by asubstance. A light absorption substance in the optical path must bepurged to several ppm order or less. This also applied to moisture,which must be removed to the ppm order or less.

To ensure the transmittance and stability of ultraviolet rays, theultraviolet path of a reticle stage or the like in the exposureapparatus is purged with inert gas. For example, Japanese PatentLaid-Open No. 6-260385 discloses a method of spraying inert gas to aphotosensitive substrate, which is not enough to purge oxygen ormoisture. Japanese Patent Laid-Open No. 8-279458 discloses a method ofcovering the whole space from the lower end of a projection opticalsystem to the vicinity of a photosensitive substrate with a sealingmember. However, the stage is difficult to move, and this method is notpractical. Japanese Patent Application No. 2000-179590 discloses amethod of disposing a cover for covering the ultraviolet path from thereticle-side lower end of an illumination optical system to the vicinityof a reticle stage, and spraying inert gas into the cover. However,oxygen or moisture cannot be sufficiently purged because the space froma reticle holder for holding a reticle to a reticle surface plate forsupporting a reticle stage is not surrounded. In addition, a sheet glassis set on the reticle stage side serving as a movable portion, whichincreases the weight of the reticle stage. Since the scan stroke rangeof the reticle stage must be covered with the sheet glass, a large sheetglass is required to further increase the weight. The sheet glassdeforms by driving of the reticle stage, changing the opticalcharacteristics. Particularly when the sheet glass functions as anoptical element, changes in optical characteristics typically appear. Inthis case, the optical characteristics must be uniform within the scanstroke range, resulting in a very complicated process. Connection of aninert gas supply tube to the reticle stage side serving as a movableportion transmits vibrations from the tube. Scan operation while thetube is connected degrades the control characteristics of the reticlestage.

As described above, an exposure apparatus using an ultraviolet ray,particularly, an ArF excimer laser beam or fluorine (F₂) excimer laserbeam suffers from large absorption of light of this wavelength by oxygenand moisture. To obtain a sufficient transmittance and stability of anultraviolet ray, the oxygen and moisture concentrations in the opticalpath must be reduced.

From this, demands have arisen for the development of an effective purgesystem for the ultraviolet light path in the exposure apparatus,particularly for the vicinity of a wafer and reticle which are oftenloaded/unloaded into/from the exposure apparatus.

SUMMARY OF THE INVENTION

The present invention has been made to overcome the conventionaldrawbacks, and has as its object to provide a device for effectivelypurging, e.g., part of the optical path with inert gas in an exposureapparatus for projecting a reticle pattern onto a photosensitivesubstrate via a projection optical system, a semiconductor devicemanufacturing method using the apparatus, a manufacturing factory, and amaintenance method therefor.

According to the first aspect of the present invention, the foregoingobject is attained by providing an exposure apparatus comprising areticle stage which holds a reticle, a reticle surface plate whichsupports the reticle stage, a projection optical system which projects apattern of the reticle onto a substrate, a shield which surrounds aspace between the reticle stage and the reticle surface plate throughwhich exposure light passes and shields the space from outside, and agas supply which supplies inert gas into the space shielded by theshield.

In the preferred embodiment, the shield is supported by the reticlestage. The shield is preferably arranged to allow movement of thereticle stage on the reticle surface plate. The shield can be formedfrom a plate member. The shield can include an air curtain or ahydrostatic bearing disposed between the reticle stage and the reticlesurface plate.

In the preferred embodiment, the inert gas supplied to the hydrostaticbearing is also supplied to the space shielded by the shield to purgethe space.

It is preferable that the apparatus mentioned above further comprises asheet glass set on the reticle surface plate so as to separate, from thespace shielded by the shield, a space inside an opening which is formedin the reticle surface plate to transmit exposure light.

It is preferable that the apparatus mentioned above further comprises asecond gas supply which supplies inert gas to the space separated by thesheet glass.

It is preferable that the apparatus mentioned above further comprises agas recovery which recovers gas from the space shielded by the shield.

It is preferable that the apparatus mentioned above further comprises asensor arranged to measure a pressure in the space shielded by theshield and a controller arranged to control the gas supply on the basisof the pressure measured by the sensor.

It is preferable that the apparatus mentioned above further comprises acleaning gas supply which supplies cleaning gas into the space shieldedby the shield. The cleaning gas can include at least one of oxygen andozone.

The apparatus can further comprise an illumination optical system and anenclosure which surrounds a space between the illumination opticalsystem and the reticle stage through which exposure light passes. It ispreferable that the enclosure is arranged such that a gap is providedbetween a lower end thereof and the reticle stage, and the reticle stagehas, around the reticle, a top plate with a surface flush with an uppersurface of the reticle.

The apparatus can further comprise a substrate stage which holds thesubstrate and an enclosure which surrounds a space between theprojection optical system and the substrate stage through which exposurelight passes. It is preferable that the enclosure is arranged such thata gap is provided between a lower end thereof and the substrate stage,and the substrate stage has, around the substrate, a top plate with asurface flush with an upper surface of the substrate.

In the preferred embodiment, the shield is so arranged as to prevent anopening of the reticle surface plate from deviating from a regiondefined by the shield.

According to the second aspect of the present invention, the foregoingobject is attained by providing an exposure apparatus comprising areticle stage which holds a reticle, a reticle surface plate whichsupports the reticle stage, the reticle surface plate having an openingfor transmitting exposure light, a projection optical system whichprojects a pattern of the reticle onto a substrate, and a sheet glassset on the reticle surface plate so as to separate a space inside theopening of the reticle surface plate from a space above the reticlesurface plate.

According to the third aspect of the present invention, the foregoingobject is attained by providing an exposure apparatus comprising anoptical system, a stage which moves with a flat object during exposure,and an enclosure which surrounds a space between the optical system andthe stage through which exposure light passes. The enclosure is arrangedsuch that a gap is provided between a lower end thereof and the stage,and the stage has, around the flat object, a top plate with a surfaceflush with an upper surface of the flat object.

The optical system may be an illumination optical system, and the stagemay be a reticle stage. Alternatively, the optical system may be aprojection optical system, and the stage may be a substrate stage.

According to the fourth aspect of the present invention, the foregoingobject is attained by providing a device manufacturing method comprisingthe steps of installing, in a semiconductor manufacturing factory,manufacturing apparatuses, for performing various processes, includingthe above exposure apparatus, and manufacturing a semiconductor deviceby performing a plurality of processes using the manufacturingapparatuses.

It is preferable that the method mentioned above further comprises thesteps of connecting the manufacturing apparatuses via a local areanetwork and communicating information about at least one of themanufacturing apparatuses between the local area network and an externalnetwork outside the semiconductor manufacturing factory.

It is preferable that the method mentioned above further comprises thestep of accessing a database provided by a vendor or user of theexposure apparatus via the external network, thereby obtainingmaintenance information of the exposure apparatus by data communication.

It is preferable that the method mentioned above further comprises thestep of performing data communication between the semiconductormanufacturing factory and another semiconductor manufacturing factoryvia the external network, thereby performing production management.

According to the fifth aspect of the present invention, the foregoingobject is attained by providing a semiconductor manufacturing factorycomprising: manufacturing apparatuses, for performing various processes,including the above exposure apparatus; a local area network forconnecting the manufacturing apparatuses; and a gateway for allowingaccess to an external network outside the factory from the local areanetwork, wherein information about at least one of the manufacturingapparatuses is communicated.

According to the sixth aspect of the present invention, the foregoingobject is attained by providing a maintenance method for the aboveexposure apparatus that is installed in a semiconductor manufacturingfactory, comprising the steps of: making a vendor or user of theexposure apparatus provide a maintenance database connected to anexternal network outside the semiconductor manufacturing factory;allowing access to the maintenance database from the semiconductormanufacturing factory via the external network; and transmittingmaintenance information accumulated in the maintenance database to thesemiconductor manufacturing factory via the external network.

It is preferable that the apparatus further comprises a display, anetwork interface and a computer for executing network software, and thedisplay, the network interface, and the computer enable communicatingmaintenance information of the exposure apparatus via a computernetwork.

In the preferred embodiment, the network software provides on thedisplay the user interface for accessing a maintenance database providedby a vendor or user of the exposure apparatus and connected to theexternal network outside a factory in which the exposure apparatus isinstalled, and information is obtained from the database via theexternal network.

Other features and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1A is a schematic view showing a projection exposure apparatusaccording to the first embodiment of the present invention;

FIG. 1B is a sectional view taken along the line B—B in FIG. 1A;

FIG. 1C is a sectional view taken along the line C—C in FIG. 1A;

FIG. 2A is a schematic view showing a projection exposure apparatusaccording to the second embodiment of the present invention;

FIG. 2B is a sectional view taken along the line B—B in FIG. 2A;

FIG. 2C is a sectional view taken along the line C—C in FIG. 2A;

FIG. 3A is a schematic view showing a projection exposure apparatusaccording to the third embodiment of the present invention;

FIG. 3B is a sectional view taken along the line B—B in FIG. 3A;

FIG. 3C is a sectional view taken along the line C—C in FIG. 3A;

FIG. 4 is a schematic view showing the structure of a projectionexposure apparatus around a reticle according to the fourth embodimentof the present invention;

FIG. 5 is a flow chart showing projection exposure operation accordingto the fifth embodiment of the present invention;

FIG. 6A is a schematic view showing a structure of a projection exposureapparatus around a reticle according to the sixth embodiment of thepresent invention;

FIG. 6B is a schematic view showing another structure of the projectionexposure apparatus around the reticle according to the sixth embodimentof the present invention;

FIG. 7 is a view showing a semiconductor device production systemaccording to the present invention when viewed from a given angle;

FIG. 8 is a view showing the semiconductor device production systemaccording to the present invention when viewed from another angle;

FIG. 9 is a view showing an example of a user interface in the exposureapparatus of the present invention;

FIG. 10 is a flow chart showing a semiconductor device manufacturingprocess;

FIG. 11 is a flow chart showing a wafer process (step 4) in detail; and

FIG. 12 is a view schematically showing a mechanism of mixing cleaninggas in inert gas.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An exposure apparatus according to the present invention is not limitedexcept for arrangements defined by the appended claims.

Ultraviolet rays as exposure light used in the exposure apparatus of thepresent invention are not specifically limited. A purge system accordingto the present invention is particularly effective for an ArF excimerlaser with a wavelength around far ultraviolet rays, particularly, 193nm, and a fluorine (F₂) excimer laser with a wavelength around 157 nm,as described above.

Preferred embodiments of the present invention will be described belowwith reference to the accompanying drawings.

<First Embodiment>

FIG. 1A shows the main part of a step & scan type projection exposureapparatus according to the first embodiment of the present invention.FIGS. 1B and 1C are sectional views of the exposure apparatus in FIG. 1Ataken along the lines B—B and C—C, respectively. In FIGS. 1A to 1C,ultraviolet rays which have reached an illumination optical system 1 inthe exposure apparatus from an ultraviolet source (not shown) irradiatea reticle 6 held by a reticle holder 13 on a reticle stage 7. A cover 3serving as an enclosure for surrounding the ultraviolet path andshielding it from the surroundings extends from the reticle-side lowerend of the illumination optical system 1 toward the vicinity of thereticle stage 7. Supply portions (including, e.g., a flow path andnozzle) 2 for supplying purge gas made of inert gas into the cover 3 areformed. The gap between the lower end of the cover 3 and the reticle 6is S1. Inert gas such as nitrogen, helium, or argon is supplied from theillumination optical system 1 into the cover 3 via the gas supplyportions 2 to purge an exposure obstacle such as oxygen or moisture.

A top plate 8 is mounted on the reticle stage 7 so as to be flush withthe upper surface of the reticle 6. This prevents the reticle stage 7from shifting from a portion effectively purged by the cover 3 even ifthe reticle stage 7 moves by a scan operation. The impurity inside thecover 3 can be satisfactorily removed. It is more desirable to surrounda purge area 9 outside the cover 3 with another cover or the like, purgethe purge area 9, and remove the impurity to a given degree. With thisarrangement, the impurity inside the cover 3 can be removed to a lowerconcentration. An example of the purge area 9 can be a space defined bya chain double-dashed line.

A linear motor stator 12 is attached to a reticle stage travelingsurface 11 on a reticle surface plate 10 for supporting the reticlestage 7. The reticle stage 7 moves while being guided by the linearmotor stator 12. A chuck groove 15 is formed in the periphery of areticle chuck surface 14 of the reticle holder 13 on the reticle stage7. The reticle 6 is set on the reticle chuck surface 14 while the entireperiphery of the reticle 6 is in contact with the reticle chuck surface14 (note that no problem occurs even if part of the reticle chucksurface 14 is notched and part of the reticle 6 is not in contact withthe reticle chuck surface 14 as far as the gap is small). The inside ofthe reticle chuck surface 14 of the reticle holder 13 and the center ofthe reticle stage 7 are opened as a space so as to transmit an exposurelight beam. The center of the reticle surface plate 10 is also opened totransmit an exposure light beam. The reticle surface plate 10 has gassupply portions 16 for supplying purge gas made of inert gas.

An enclosure 17 serving as a shield for schematically shielding theopening of the reticle stage and the opening of the reticle surfaceplate from the surroundings is attached to the reticle surface plateside of the opening of the reticle stage. The gap between the lower endof the enclosure 17 and the reticle surface plate 10 is S2. Theenclosure 17 is so arranged as to prevent the opening of the reticlesurface plate from deviating from the internal region defined by theenclosure 17 during scan exposure.

As a conceivable example of the enclosure 17, the opening of the reticlestage 7 is surrounded by a cover (e.g., plate member) attached to thereticle stage 7, the opening of the reticle stage 7 is surrounded by ahydrostatic bearing 18 for guiding the reticle stage 7, or the openingof the reticle stage 7 is surrounded by a cover and one or morehydrostatic bearings 18 (FIG. 1C). A preferable cover is one made of ametal such as stainless steel or one made of a resin such asfluoroplastics. The enclosure 17 may be implemented by an air curtainusing inert gas.

Purge gas made of inert gas is supplied into a space defined by thereticle 6, the reticle stage 7, the reticle surface plate 10, theenclosure 17, and a projection optical system 19 via the gas supplyportions 16 formed in the reticle surface plate 10. It is also possibleto purge the space by using only inert gas supplied to the hydrostaticbearing 18 without forming the gas supply portions 16.

Ultraviolet rays having passed through the reticle 6 irradiate a wafer21 on a wafer stage 20 via the projection optical system 19. Theprojection optical system 19 has a cover 22 serving as an enclosurewhich extends from the wafer-side lower end of the projection opticalsystem 19 toward the vicinity of the wafer stage 20 and shields theultraviolet path from the surroundings. Nozzles 23 serving as supplyports for supplying purge gas made of inert gas into the cover 22 arearranged. Inert gas such as nitrogen, helium, or argon is supplied fromthe projection optical system 19 into the cover 22 via the nozzles 23 topurge an exposure obstacle such as oxygen or moisture. The gap betweenthe lower end of the cover 22 and the wafer 21 is S3.

A top plate 24 is mounted on the wafer stage 20 to be flush with thewafer 21. This prevents the wafer stage 20 from shifting from a portioneffectively purged by the cover 22 even if the wafer stage 20 moves by ascan operation.

The impurities inside the cover 22 can be satisfactorily removed. It ismore desirable to purge a purge area 25 outside the cover 22 and removethe impurities to a certain degree. In this case, the impurities insidethe cover 22 can be removed to a lower concentration. An example of thepurge area 25 is a space defined by a projection optical system surfaceplate 26, wafer stage surface plate 27, and partition 28.

To prevent transmission of vibrations or deformation from the waferstage surface plate 27 to the projection optical system surface plate26, the partition 28 is formed from a bellows-like elastic member.Alternatively, it may also be possible to form the partition 28 from ageneral rigid member instead of the bellows structure, and form a smallgap in the whole periphery between the partition 28 and the projectionoptical system surface plate 26 without coupling the partition 28 to theprojection optical system surface plate 26. Since the amount of purgegas increases because purge gas leaks from this gap, no vibrations ordeformation transmits. Alternatively, it may also be possible to omit astage damper 29, form the partition 28 from a general rigid memberinstead of the bellows structure, and integrally suspend the wafer stagesurface plate 27 from the projection optical system surface plate 26 bythe partition 28.

In the exposure apparatus of the first embodiment, the impurity in theoptical path of a fluorine gas laser light can be purged even with theuse of a fluorine gas laser light for exposure light, thereby ensuring asatisfactory transmittance and stability. By connecting an inert gassupply tube to the reticle surface plate 10, the control characteristicsof the reticle stage 7 can be improved because no vibrations from thetube transmit to the reticle stage 7.

<Second Embodiment>

FIG. 2A shows the main part of a step and scan type projection exposureapparatus according to the second embodiment of the present invention.FIGS. 2B and 2C are sectional views of the exposure apparatus shown inFIG. 2A taken along the lines B—B and C—C, respectively. In the secondembodiment, a sheet glass 30 is attached to the opening of a reticlesurface plate 10 in place of the enclosure 17 described in the firstembodiment. A first space 100 is defined by a reticle 6, a reticle stage7, the reticle surface plate 10, and the sheet glass 30. A second space200 is defined by the reticle surface plate 10, the sheet glass 30, anda projection optical system 19. The sheet glass 30 is laid out such thatits upper surface (i.e., the surface on the reticle stage 7 side) isflush with the upper surface (i.e., the surface on the reticle stage 7side) of the reticle surface plate 10. By reducing the step in thismanner, the optical path extending from the lower surface of the reticlestage 7 to the projection optical system 19 is hardly disturbed by ascan operation of the reticle stage 7. Accordingly, the concentrationsof the impurities which absorb ultraviolet rays stabilize, and spatialand temporal changes in exposure amount further stabilize. The sheetglass 30 may be an optical element for correcting the opticalcharacteristics of exposure light. Conceivable examples of the sheetglass 30 are a spherical lens such as a concave, convex, or cylindricallens, an aspherical lens, and an optical element whose plane hasundergone partial aspherical processing. The sheet glass 30 ispreferably so attached as to easily exchange it when contaminants aredeposited on the surface. The reticle surface plate 10 has gas supplyportions 16 for supplying purge gas made of inert gas into the first andsecond spaces 100 and 200. The remaining arrangement is the same as thatin the first embodiment.

In the exposure apparatus of the second embodiment, the first and secondspaces 100 and 200 are purged even if the reticle stage 7 moves by ascan operation since this exposure apparatus does not require anyenclosure 17 attached to the reticle stage 7, unlike the firstembodiment, the reticle stage 7 can be simplified. Since the sheet glass30 is set on the reticle surface plate 10 serving as a stationaryportion, the reticle stage 7 can be further simplified without anydeformation of the sheet glass 30 caused by driving of the stage or anychanges in optical characteristics.

<Third Embodiment>

FIG. 3A shows the main part of a step & scan type projection exposureapparatus according to the third embodiment of the present invention.FIGS. 3B and 3C are sectional views of the exposure apparatus in FIG. 3Ataken along the lines B—B and C—C, respectively. The third embodimentadopts both an enclosure 17 as in the first embodiment and a sheet glass30 as in the second embodiment. A reticle surface plate 10 has gassupply portions 16 for supplying purge gas made of inert gas into aspace 110 defined by a reticle 6, a reticle stage 7, a reticle surfaceplate 10, the enclosure 17, and the sheet glass 30, and a space 210defined by the reticle surface plate 10, the sheet glass 30, and aprojection optical system 19. The remaining arrangement is the same asthat in the first embodiment.

In the exposure apparatus of the third embodiment, the purge areabetween the reticle 6 and the projection optical system 19 is divided.As a result, the concentration distribution of the impurities whichabsorb a fluorine gas laser beam stabilizes, and spatial and temporalchanges in exposure amount become smaller and stable. Since the space inthe opening of the reticle stage 7 can hold high airtightness, theconcentrations of the impurities which absorb a fluorine gas laser beamare further suppressed to increase the transmittance, and theconcentration distribution further stabilizes to reduce and stabilizespatial and temporal changes in exposure amount. Moreover, theconsumption amount of purge gas can be reduced, and the purge time untilthe impurities in the purge area decreases to predeterminedconcentrations or less can be shortened.

<Fourth Embodiment>

FIG. 4 is a view showing a structure from the illumination opticalsystem to reticle surface plate of an exposure apparatus according tothe fourth embodiment. In the fourth embodiment, a supply port 31 forsupplying purge gas is formed on one side of a reticle surface plate 10in the third embodiment, and a recovery port 32 for recovering purge gasis formed on the other side of the reticle surface plate 10, therebypurging a purge area 110 with purge gas. This can also be applied to thefirst and second embodiments. Purge gas is supplied from the supply port31 to the vicinity of a reticle in a direction indicated by an arrow. Atthe same time the purge gas is recovered from a recovery port 32.Exposure light enters a projection optical system via a sheet glass 30.The direction in which purge gas flows may be parallel, perpendicular,or oblique to the scan direction, or may change together with the scan.The purge gas direction is desirably perpendicular to the scan directionso as not to generate any exposure difference in the scan direction.

In the exposure apparatus of the fourth embodiment, the impurities inthe optical path of a fluorine gas laser can be purged even with the useof a fluorine gas laser for exposure light, thereby ensuring asatisfactory transmittance and stability of exposure light. In addition,the supply and recovery ports are formed to positively generate the flowof purge gas from the supply port to the recovery port. This can preventcontamination in the purge area owing to residence of the purge gas inthe purge area.

<Fifth Embodiment>

FIG. 5 is a flow chart in a case wherein inert gas flows only when awafer and/or reticle is loaded below a cover 3 and/or cover 22 in orderto save the amount of inert gas in the first to fourth embodiments.Similarly, the presence/absence of top plates 8 and 24 is alsoconsidered, and inert gas is saved by flowing inert gas only when a topplate is loaded.

<Sixth Embodiment>

The sixth embodiment employs pressure sensors within covers 3 and 22 inthe exposure apparatuses of the first to fifth embodiments, and adopts apurge gas supply unit having a function of controlling the gas pressurein a purged space. The purge gas pressure in the space is controlled toa constant value regardless of the space on the basis of pressure valuesmeasured by the pressure sensors.

The effects unique to this arrangement will be explained. The interiorof the lens barrel of an illumination optical system 1 or projectionoptical system 19 is also purged to an almost sealed system with inertgas in order to remove the impurity. The interior of the lens barrelmaintains an almost constant pressure without following externalpressure variations. For this reason, a pressure difference is generatedbetween the inside and outside of the lens barrel in accordance with thepressure variations outside the lens barrel. Then, an optical elementbelow the illumination optical system 1 or projection optical system 19deforms in accordance with the pressure difference, and the opticalperformance changes in accordance with the pressure variations. However,by controlling the purge gas pressures inside the covers 3 and 22 belowthese optical elements to constant values, the sixth embodiment canprevent generation of any pressure difference and can suppress changesin optical performance caused by the pressure variations.

FIG. 6A shows an embodiment in which pressure sensors 33 are arrangedinside the cover 3 and inside the reticle stage 7 or the opening of thereticle surface plate 10 in the first embodiment, and a purge gas supplyunit 34 having a function of controlling the purge gas pressure isdisposed upstream of the gas supply portion 16. The purge gas supplyunit 34 controls the purge gas pressure on the basis of pressure valuesmeasured by the pressure sensors 33, and thus controls purge gaspressures inside the covers 3 and 22 regardless of the externalpressure.

FIG. 6B shows an embodiment in which pressure sensors 33 are arranged atthree portions, i.e., inside the cover 3, inside the reticle stage 7,and above the projection optical system 19 in the third embodiment, anda purge gas supply unit 34 having a function of controlling the purgegas pressure is adopted. When a sheet glass 30 is attached to thereticle surface plate 10, like this embodiment, purge gas pressures in aspace 100 inside the reticle stage 7 and a space 200 above theprojection optical system 19 are controlled to constant values. Nopressure difference is generated between the spaces 100 and 200, thesheet glass 30 does not deform, and changes in optical performance canbe suppressed. Furthermore, purge gas pressures in a space 300 and thespace 100 above and below the reticle 6 also keep constant withoutgenerating any pressure difference between them, and the reticle 6 doesnot deform.

If the flexure of the reticle 6 by its weight or its flatness causesdefocus or distortion, the purge gas pressure in the internal space ofthe reticle stage 7 defined by the reticle 6, the reticle stage 7, anenclosure 17, the reticle surface plate 10, and the sheet glass 30 iscontrolled to an optimal known value, thereby deforming the reticle 6 orsheet glass 30 by a predetermined amount. As a result, defocus ordistortion can be reduced. The optimal pressure is a pressure whichminimizes defocus and distortion checked by performing exposure using adesired reticle 6 in advance while changing the purge gas pressure.Alternatively, the optimal pressure may be obtained by simulationcalculation.

<Seventh Embodiment>

In the first to sixth embodiments, purge gas made of inert gas such asnitrogen, helium, or argon is supplied through each nozzle. An exposureapparatus according to the seventh embodiment also comprises a mechanismof mixing cleaning gas such as oxygen (O₂) and/or ozone (O₃) in theinert gas.

A detailed arrangement will be described with reference to FIG. 12. Innormal exposure, a valve 1202 is closed to prevent mixing of oxygenand/or ozone, and a valve 1201 is opened to supply only inert gas intoan optical path, i.e., a purge area through a gas supply portion 16. Ina standby state in which the exposure apparatus is inactive, duringnormal exposure at a designated time interval, or in a case wherein areticle is set on the reticle stage, the valve 1202 is opened to mix asmall amount of oxygen and/or ozone in the inert gas and to purge thepurge area. Without loading any wafer, a dummy exposure operation isdone for a predetermined time or until a prescribed illuminance at theimage plane is attained. After that, mixing of oxygen and/or ozone isstopped. Only inert gas is supplied for purge, and a normal exposureoperation is executed.

The effects unique to this arrangement will be explained.Short-wavelength exposure light such as far ultraviolet rays,particularly, an ArF excimer laser beam or fluorine excimer laser beamdecomposes an impurity such as organic molecules in the air. Thedecomposition product is deposited on an optical element. The surface ofthe optical element bears a carbon film, a carbon-containing film, or adeposit of the organic compound. The transmittance of the opticalelement gradually decreases to decrease the illuminance at the imageplane, resulting in low throughput. In the above embodiments, thevicinity in low throughput. In the above embodiments, the vicinity ofthe reticle 6 or wafer 21 is purged with inert gas to minimize theimpurity concentration, but a small amount of impurities may remain. Forexample, degassing may occur from a resist applied to the wafer 21 or anadhesive layer between the resist and the wafer 21 during or beforeexposure, and an impurity may exist near a sheet glass 35 below theprojection optical system 19. Also, the reticle 6 with a small amount ofimpurities may be loaded and part of the impurities may evaporate, ordegassing may occur from an adhesive layer between the reticle 6 and apellicle frame or an adhesive layer between the pellicle frame and apellicle 5, and the impurities may exist near a sheet glass 4 below theillumination optical system 1, the sheet glass 30 of the reticle surfaceplate 10, or the surface of an optical element above the projectionoptical system 19. In these cases, the organic compound decomposed andproduced by exposure is deposited on optical elements, and thetransmittance gradually decreases. To prevent this, these opticalelements are illuminated with exposure light during purge while a smallamount of ozone is mixed in inert gas. The deposited organic compound isoxidized and decomposed by a so-called ozone cleaning effect, anddeposition of the decomposition product is prevented. Alternatively, theoptical elements are illuminated with exposure light during purge whilea small amount of oxygen is mixed in the inert gas. Then, oxygen isconverted into ozone by a photochemical reaction, obtaining the sameozone cleaning effect as that of a mixture of ozone. Periodic executionof this processing can prevent a decrease in illuminance at the imageplane and can always maintain high throughput.

<Embodiment of Semiconductor Production System>

A production system for a semiconductor device (e.g., a semiconductorchip such as an IC or LSI, a liquid crystal panel, CCD, a thin-filmmagnetic head, a micromachine, or the like) will be exemplified. Atrouble remedy or periodic maintenance of a manufacturing apparatusinstalled in a semiconductor manufacturing factory, or maintenanceservice such as software distribution is performed by using a computernetwork outside the manufacturing factory.

FIG. 7 shows the overall system cut out at a given angle. In FIG. 7,reference numeral 101 denotes a business office of a vendor (apparatussupply manufacturer) which provides a semiconductor device manufacturingapparatus. Assumed examples of the manufacturing apparatus aresemiconductor manufacturing apparatuses for performing various processesused in a semiconductor manufacturing factory, such as pre-processapparatuses (e.g., a lithography apparatus including an exposureapparatus, a resist processing apparatus, and an etching apparatus, anannealing apparatus, a film formation apparatus, an inspectionapparatus, and the like). The business office 101 comprises a hostmanagement system 108 for providing a maintenance database for themanufacturing apparatus, a plurality of operation terminal computers110, and a LAN (Local Area Network) 109 which connects the hostmanagement system 108 and computers 110 to construct an intranet. Thehost management system 108 has a gateway for connecting the LAN 109 toInternet 105 as an external network of the business office, and asecurity function for limiting external accesses.

Reference numerals 102 to 104 denote manufacturing factories of thesemiconductor manufacturer as users of manufacturing apparatuses. Themanufacturing factories 102 to 104 may belong to different manufacturersor the same manufacturer (e.g., a pre-process factory, a post-processfactory, and the like). Each of the factories 102 to 104 is equippedwith a plurality of manufacturing apparatuses 106, a LAN (Local AreaNetwork) 111 which connects these apparatuses 106 to construct anintranet, and a host management system 107 serving as a monitoringapparatus for monitoring the operation status of each manufacturingapparatus 106. The host management system 107 in each of the factories102 to 104 has a gateway for connecting the LAN 111 in the factory tothe Internet 105 as an external network of the factory. Each factory canaccess the host management system 108 of the vendor 101 from the LAN 111via the Internet 105. The security function of the host managementsystem 108 authorizes access of only a limited user. More specifically,the factory notifies the vendor via the Internet 105 of statusinformation (e.g., the symptom of a manufacturing apparatus in trouble)representing the operation status of each manufacturing apparatus 106.The factory can receive, from the vendor, response information (e.g.,information designating a remedy against the trouble, or remedy softwareor data) corresponding to the notification, or maintenance informationsuch as the latest software or help information. Data communicationbetween the factories 102 to 104 and the vendor 101 and datacommunication via the LAN 111 in each factory adopt a communicationprotocol (TCP/IP) generally used in the Internet. Instead of using theInternet as an external network of the factory, a dedicated-line network(e.g., ISDN) having high security which inhibits access of a third partycan be adopted. It is also possible that the user constructs a databasein addition to one provided by the vendor and sets the database on anexternal network and that the host management system authorizes accessto the database from a plurality of user factories.

FIG. 8 is a view showing the concept of the overall system of thisembodiment that is cut out at a different angle from FIG. 7. In theabove example, a plurality of user factories having manufacturingapparatuses and the management system of the manufacturing apparatusvendor are connected via an external network, and production managementof each factory or information of at least one manufacturing apparatusis communicated via the external network. In the example of FIG. 8, afactory having manufacturing apparatuses of a plurality of vendors, andthe management systems of the vendors for these manufacturingapparatuses are connected via the external network of the factory, andmaintenance information of each manufacturing apparatus is communicated.In FIG. 8, reference numeral 201 denotes a manufacturing factory of amanufacturing apparatus user (semiconductor device manufacturer) wheremanufacturing apparatuses for performing various processes, e.g., anexposure apparatus 202, a resist processing apparatus 203, and a filmformation apparatus 204 are installed in the manufacturing line of thefactory. FIG. 8 shows only one manufacturing factory 201, but aplurality of factories are networked in practice. The respectiveapparatuses in the factory are connected to a LAN 206 to construct anintranet, and a host management system 205 manages the operation of themanufacturing line. The business offices of vendors (apparatus supplymanufacturers) such as an exposure apparatus manufacturer 210, a resistprocessing apparatus manufacturer 220, and a film formation apparatusmanufacturer 230 comprise host management systems 211, 221, and 231 forexecuting remote maintenance for the supplied apparatuses. Each hostmanagement system has a maintenance database and a gateway for anexternal network, as described above. The host management system 205 formanaging the apparatuses in the manufacturing factory of the user, andthe management systems 211, 221, and 231 of the vendors for therespective apparatuses are connected via the Internet or dedicated-linenetwork serving as an external network 200. If a trouble occurs in anyone of a series of manufacturing apparatuses along the manufacturingline in this system, the operation of the manufacturing line stops. Thistrouble can be quickly solved by remote maintenance from the vendor ofthe apparatus in trouble via the Internet 200. This can minimize thestop of the manufacturing line.

Each of the manufacturing apparatuses in the semiconductor manufacturingfactory comprises a display, a network interface, and a computer forexecuting network access software and apparatus operating software whichare stored in a storage device. The storage device is a built-in memory,hard disk, or network file server. The network access software includesa dedicated or general-purpose web browser, and provides a userinterface having a window as shown in FIG. 9 on the display. Whilereferring to this window, the operator who manages manufacturingapparatuses in each factory inputs, in input items on the windows,pieces of information such as the type of manufacturing apparatus (401),serial number (402), subject of trouble (403), occurrence data (404),degree of urgency (405), symptom (406), remedy (407), and progress(408). The pieces of input information are transmitted to themaintenance database via the Internet, and appropriate maintenanceinformation is sent back from the maintenance database and displayed onthe display. The user interface provided by the web browser realizeshyperlink functions (410 to 412), as shown in FIG. 9. This allows theoperator in the factory to access detailed information of each item,receive the latest-version software to be used for a manufacturingapparatus from a software library provided by a vendor, and receive anoperation guide (help information) as a reference for the operator inthe factory. The maintenance information provided by the maintenancedatabase also includes information about the features of the presentinvention described above. The software library also provides thelatest-version software for implementing the features of the presentinvention.

A semiconductor device manufacturing process using the above-describedproduction system will be explained. FIG. 10 shows the flow of the wholemanufacturing process of the semiconductor device. In step 1 (circuitdesign), a semiconductor device circuit is designed. In step 2 (maskformation), a mask having a designed circuit pattern is formed. In step3 (wafer manufacture), a wafer is manufactured using a material such assilicon. In step 4 (wafer process) called a pre-process, an actualcircuit is formed on the wafer by lithography using the prepared maskand wafer. Step 5 (assembly) called a post-process is the step offorming a semiconductor chip by using the wafer manufactured in step 4,and includes an assembly process (dicing and bonding) and a packagingprocess (chip encapsulation). In step 6 (inspection), inspections suchas the operation confirmation test and durability test of thesemiconductor device manufactured in step 5 are conducted. After thesesteps, the semiconductor device is completed and shipped (step 7). Thepre-process and post-process are performed in separate dedicatedfactories, and maintenance is done for each of the factories by theabove-described remote maintenance system. Information for productionmanagement and apparatus maintenance is communicated between thepre-process factory and the post-process factory via the Internet ordedicated-line network.

FIG. 11 shows the detailed flow of the wafer process. In step 11(oxidation), the wafer surface is oxidized. In step 12 (CVD), aninsulating film is formed on the wafer surface. In step 13 (electrodeformation), an electrode is formed on the wafer by vapor deposition. Instep 14 (ion implantation), ions are implanted in the wafer. In step 15(resist processing), a photosensitive agent is applied to the wafer. Instep 16 (exposure), the above-mentioned exposure apparatus exposes thewafer to the circuit pattern of the mask. In step 17 (developing), theexposed wafer is developed. In step 18 (etching), the resist is etchedexcept for the developed resist image. In step 19 (resist removal), anunnecessary resist after etching is removed. These steps are repeated toform multiple circuit patterns on the wafer. A manufacturing apparatusused in each step undergoes maintenance by the remote maintenancesystem, which prevents trouble in advance. Even if trouble occurs, themanufacturing apparatus can be quickly recovered. The productivity ofthe semiconductor device can be increased in comparison with the priorart.

As has been described above, according to the present invention, oxygenand moisture can be partially, effectively purged near a reticle and/orwafer in an exposure apparatus using ultraviolet rays, particularly, anArF excimer laser beam or a fluorine (F₂) excimer laser beam can beobtained. This realizes high-precision projection exposure andsatisfactory projection of a fine circuit pattern.

As many apparently widely different embodiments of the present inventioncan be made without departing from the spirit and scope thereof, it isto be understood that the invention is not limited to the specificembodiments thereof except as defined in the appended claims.

1. An exposure apparatus for exposing a substrate to light via a patternof a reticle, said apparatus comprising: a reticle stage configured tohold the reticle and to move; a projection optical system configured toproject the pattern onto the substrate; a base plate disposed betweensaid reticle stage and said projection optical system, configured tosupport said reticle stage and having an opening for the light to pass;a sheet glass held by said base plate, disposed at the opening andconfigured to transmit the light; and a supply system configured tosupply an inert gas to a space partitioned by said projection opticalsystem, said base plate and said sheet glass, said supply system havinga port which faces toward a direction substantially perpendicular to anoptical axis of said projection optical system, the inert gas beingsupplied from said port.
 2. A method of manufacturing a device, saidmethod comprising steps of: exposing a substrate to light via a patternof a reticle using an exposure apparatus as defined in claim 1;developing the exposed substrate; and processing the developed substrateto manufacture the device.
 3. An exposure apparatus for exposing asubstrate to light via a pattern of a reticle, said apparatuscomprising: a reticle stage configured to hold the reticle and to move;a projection optical system configured to project the pattern onto thesubstrate; a base plate disposed between said reticle stage and saidprojection optical system, configured to support said reticle stage andhaving an opening for the light to pass; a sheet glass held by said baseplate, disposed at the opening and configured to transmit the light; anda supply system configured to supply an inert gas to a space partitionedby said projection optical system, said base plate, and said sheetglass, said supply system having a port in said base plate, the inertgas being supplied from said port.
 4. A method of manufacturing adevice, said method comprising steps of: exposing a substrate to lightvia a pattern of a reticle using an exposure apparatus as defined inclaim 3; developing the exposed substrate; and processing the developedsubstrate to manufacture the device.
 5. An exposure apparatus forexposing a substrate to light via a pattern of a reticle, said apparatuscomprising: a reticle stage configured to hold the reticle and to move;a projection optical system configured to project the pattern onto thesubstrate; a base plate disposed between said reticle stage and saidprojection optical system, configured to support said reticle stage andhaving an opening for the light to pass; a sheet glass held by said baseplate, disposed at the opening so that an upper surface of said sheetglass is even with an upper surface of said base plate, and configuredto transmit the light; and a supply system configured to supply an inertgas to a space partitioned by said projection optical system, said baseplate, and said sheet glass, said supply system having a port disposedat a height between the upper surface of said base plate and a lowersurface of said base plate, the inert gas supplied from said port.
 6. Amethod of manufacturing a device, said method comprising steps of:exposing a substrate to light via a pattern of a reticle using anexposure apparatus as defined in claim 5; developing the exposedsubstrate; and processing the developed substrate to manufacture thedevice.